This invention relates to a vibration-damping means for a rotary annular bellows and, more particularly, to a vibration-damping means for a rotary annular bellows seal assembly.
A rotary annular bellows seal assembly is used generally to apply an axial force between two sealing members having relative rotation to each other. A rotating bellows seal assembly used with a rotating shaft usually includes an annular bellows having a plurality of axially-expandable convolutions sealingly connected at one end to the shaft and at the other end to a first seal ring, and a mating seal ring fixed from rotation with the shaft and sealingly engaging the first seal ring. The convolutions of the bellows provide a resilient bias for maintaining the seal rings in firm contact, while the bellows itself provides a sealed area around the shaft.
The satisfactory operation of a rotary bellows seal assembly requires that the mating surfaces between the seal rings be held tightly together during relative rotation to prevent leakage of a fluid or the like between the rings.
In operation, the bellows may be subjected to vibrations from different sources in addition to its natural vibration frequency. When a rotary bellows seal assembly is employed in an apparatus which is subject to vibrations, the convolutions of the bellows pick up these vibrations. For instance, a rotary shaft may pulsate due to its connection to other rotating parts of the apparatus and thus ultimately introduce vibration into the convolutions of a bellows attached to the rotary shaft.
Vibration may also be caused by a wobbling motion of the mating ring which may result from imperfect axial alignment between the seal rings. Vibration may be caused by friction between the sealing faces of the seal rings tending to impart a stick-slick motion to those faces. Vibrations may even be caused by turbulence in a fluid adjacent the bellows assembly. Such vibrations are quite frequently developed in aircraft mainshaft seals, automotive seals, pump seals, compressor seals and the like.
Whatever the source of the vibrations, when the mechanical vibrations are superimposed on the natural frequency of vibration of the convolutions of the bellows, the life of the bellows is significantly shortened due to fatigue in the convolutions resulting from excessive vibrations. Conventional mechanical vibration-damping means, such as plates, clips, and fingers, reduce the amplitude of vibration of the bellows. However, these known devices continuously rub on the inner or outer peripheries of the convolutions of the annular bellows and eventually cause failure of the bellows. These conventional vibration-damping devices are also relatively complex, expensive, or difficult to maintain due to their elaborate configuration or the materials from which they are made.